First-order estimation of in-place natural gas resources at the Nyegga gas hydrate prospect, mid-Norwegian Margin

Abstract

Gas hydrates are solid compounds of a guest gas molecule (primarily methane) enclosed in a lattice of host water molecules, occurring under specific pressure-temperature conditions in both natural and manmade environments. In the past decade, gas hydrates are increasingly investigated as a potential new energy source.

This thesis presents an integrated evaluation of the gas bound within the hydrate province of the Nyegga area, located in the southern Norwegian Sea. Gas hydrates have long been inferred in the region on the basis of bottom simulating reflections (BSRs).

A stochastic Monte Carlo-type calculation was conducted to calculate the in-place gas bound within a gas hydrate zone, as well as within the associated free gas and chimney zones. A prospect, defined by the BSR-extent, is evaluated with focus on the uncertainty of the various reservoir parameters. The lateral variation in reservoir parameters, particularly the 3D reservoir extent and gas saturation, is poorly constrained using the available data and thus results in a large range of input parameters.

The Nyegga prospect appears to hold approximately 700 GSm3 of gas in the mean case, roughly comparable to the Ormen Lange gas field. The uncertainty related to the input parameters gives a wide spread of in-place volumes of ca. 180 GSm3 (P90) to >1400 GSm3 (P10). The majority of the resources appear to be bound in the solid gas hydrate zone, followed by the free gas zone and the chimney zone.